She said this. This is as close to an admission that you could get. She would never use that wording if this story were fabricated. She'd just say "I never said anything like that".
The "nonlegal" fluff in the emails is bs, but this story itself isnt.
It was, of course, "just a joke" much in much the same way racist jokes are "just a joke", which is why he took it seriously. It's why making a joke about murdering the president will get you hauled in by the secret service.
Arguing it's unproven is FUD. Why snopes is saying this is beyond me.
Julan Assange also participated in the creation of a video with the same group released closely afterward, which at least implies that he might share the song writers perspective.
I have tried to found a source for what the lyrics say, but at any rate it seems clear that there existed an opinion (which very likely was shared by Assange) that Hillary Clinton where out to get Assange and an active part of the US actions against him. The exact wording is "charged for high treason", which is different from a drone strike but carries the same result: Death.
In my intepretation, it seems pretty clear that Assange might have had a negative opinion about Hillary Clinton 6 years later, rather than being neutral about the whole thing. Having the perception that someone is after to kill you can have that.
(Anyone that thinks that the band is a right-wing group should check out the videos produced about Trump).
Edit: If I talked about droning Julian Assange, "it would have been a joke."
... that's a pretty weak, fence sitting, denial. That's almost saying " if the recording or memo leaks, remember I said it was a joke